1. Field of the Invention
The present invention relates to wireless communication base station devices and wireless communication systems. For example, the present invention relates to a wireless LAN base station device configured to use a plurality of communication schemes.
2. Description of the Related Art
In recent years, the Institute of Electrical and Electronics Engineers (IEEE) 802.11 committee has discussed next-generation high-speed wireless local area network (LAN) schemes. The committee has proposed a scheme of increasing a communication frequency band from 20 MHz, a conventional value, to 40 MHz to enable high-speed communications. This proposal is documented in “IEEE Standards and Information Exchange between Systems—Local and Metropolitan Area Network—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, IEEE 802.11, 1999 Edition (ISO/IEC 8802-11), 1999, and on the Internet <URL://standards.ieee.org/getieee802/802.11.html> and <URL://standards.ieee.org/getieee802/download/802.11-1999.pdf>.
The committee has also proposed a communication scheme called 20-MHz-Base Managed Mixed Mode according to which both a wireless LAN terminal for communications in a 40-MHz band and a wireless LAN terminal for communications in a 20-MHz band are accommodated in one wireless LAN base station. This scheme is documented in Adrian Stephens & Sean Coffey, “Joint Proposal: High throughput extension to the 802.11 Standard: MAC”, IEEE 802.11-05-1095-05, 2006, January and on the Internet <URL://www.802wirelessworld.com>. According to this scheme, a wireless LAN base station determines communication periods at 20 MHz and 40 MHz within one data communication cycle.
However, traffic for actual transmissions may be incompatible with the communication periods depending on the assignment of communication periods within one cycle. This disadvantageously reduces the efficiency of data transmission.